In the scope of the invention, one considers hygienic pads those absorbing devices intended to be used outside the feminine body, usually during her menstrual periods, to receive and retain menstrual and other vaginal discharges.
Disposable sanitary pads are designed to be abandoned after they have collected the fluids from the feminine body, without being used once again.
Sanitary pads are items of general consumption in modern society and, for explanatory purposes, they can be divided into three categories, namely:
tampons PA1 external pads PA1 hybrid pads, which have characteristics of the other two types.
Tampons are pads that have the capacity of intercepting menstrual discharge within the vaginal duct with little risk of soiling the user's clothes. They are considered superior protection means. In practice failures can occur in their functioning as regards their capacity of effectively having radial expansion in function of the fluid that causes expansion of the pad, thus sealing and creating occlusion within the vaginal duct. Besides, there are people who, for physical or psychological reasons, are incapable of using tampons as effective feminine protection means. Finally, they can present insertion or removal problems; sometimes they are sticky and difficult to handle, and in certain health cases there is some medical restriction.
The so-called hybrid Pads are those that incorporate characteristics of tampons and external sanitary pads. Sometimes they are called wads or labial pads or vestibule-type Pads, in which case a Partial or total insertion into the vulvar vestibule occurs.
In many of the cases described in the literature, one does not take into account the anatomical cooperation with the user's body to the effect that the sensitive tissues are often distended by the obstructive geometry of certain structural elements, that is to say, the so-called labial pads find their functioning in friction contact with very sensitive urogenital parts such as the vaginal orifice, the urethral orifice and/or the clitoris. In other cases, it is stated that a pad should be firmly fastened to the user's intimate clothes with a portion of the pad located inside the vestibule, and under most circumstances this creates a friction effect inside that sensitive part.
Thus, according to U.S. Pat. Nos. 2,092,342 and 3,905,372, an element inside the vaginal opening is physically connected to an external part, so that the relative movement between the user's body and the underlying structure of the Pad causes discomfort, irritation and even pain. In a similar way, U.S. Pat. No. 3,983,873 describes flaps that are supported against the walls of the labial space, in order to increase the retaining forces of the pad. There are other vestibule-type Pads which are designed to eliminate this irritation factor by relative movement involving body/product/user's clothes, as in U.S. Pat. No. 4,742,245; however, the disclosed Product is extremely sophisticated and is expensive to manufacture.
External sanitary pads have been developed for use outside the body near the vulvar region, to collect the menstrual fluid, other vaginal discharges and possibly urine of incontinent women.
In their simplest and more traditional form, such Pads comprise an absorbent core placed between a fluid-permeable facing sheet (sometimes referred to as a "top sheet") and a fluid-impermeable backing sheet.
The absorbent core, sometimes referred to herein as the "absorbing element", is adapted to receive and absorb the menstrual discharge and other vaginal discharges. The absorbent core may comprise comminuted wood pulp fibers, Polymer foams, vegetable pulp, natural or synthetic fibers or any other material which can absorb menstrual fluids or the like body discharges. Wood pulp fibers are commonly used as the major constituent of the absorbent core of external sanitary pads.
The fluid-permeable facing sheet contacts the wearer's body when the sanitary pad is in use and permits the menstrual or other vaginal discharge to pass therethrough so as to be absorbed by the underlying absorbent core. This facing sheet usually comprises a fluid-permeable nonwoven fabric or a perforated plastic film. Although the facing sheet may be hydrophilic in nature, it is preferred that it be hydrophobic in nature. In the latter case, the menstrual or other discharge Passes through the fluid-permeable facing sheet but the sheet, owing to its hydrophobic nature, tends to remain dry to the touch, thus making the product more comfortable in use. Perforated Plastic films are usually inherently hydrophobic. Nonwoven fabrics, if they are not made of hydrophobic fibers, can be rendered hydrophobic by treatment with, e.g. a repellent finish such as that provided by fluorochemicals, wax emulsions or the like.
The purpose of the fluid-impermeable backing sheet, as its name suggests, is to prevent the fluid collected by the absorbent core from leaking from the sanitary pad and staining the clothing of the user. The backing sheet usually comprises a thin film of plastic such as polyethylene, although in some cases it might also comprise other materials, e.g. a nonwoven fabric, which has been suitably treated so as to be liquid impermeable. If desired, the backing sheet may be moisture vapor permeable, that is, it may allow moisture vapor to pass therethrough while at the same time preventing the passage of liquids.
Leakage, and the most most common is usually leakage of menstrual blood at the sides, even in very small amounts, is a great discomfort and embarrassment for the user. For those skilled in the art, the goal aimed at in developing such products is maximization of the flow of liquid in direction Z (taking into account that, in a graph for three-dimensional representation, axes X and Y represent the horizontal plane, and axis Z is perpendicular to them), since, in addition to the technical reasons that fully justify this objective, there are psychological reasons which show that a rapid Z-directional flow minimizes the stain effect on the pad and, associated with conditions of relatively dry top sheet, it has to do with the feeling of safety, thus reducing the possibility of embarrassment due to the failure of the pad, i.e. leakage.
The external pad of the traditional type is merely an elongated rectangular product, made without any worry about the user's anatomy. Thus, when in use, such a product may undergo deformation that detracts from its performance considerably and favors frequent leakage.
Starting therefrom the improvements have followed one another until the present prior art and have resulted, either directly or indirectly, in lesser possibility of leakage:
by forming the absorbing sheets more anatomical than a rectangle, for instance in the form of an hourglass;
by causing the pad as a whole to take on the form of a shell in order to fit between the user's legs in a better manner and be closer to her perineal area;
by using top sheets that optimize the passage of liquid towards the absorbing element and restrict the return thereof in the opposite direction;
by creating more elaborate structures, for instance, an absorbing element which is thicker in its central area to bring about more proximity between the point of discharge and the pad, side flaps that form barriers for leakage, overlapped structures such as in U.S. Pat. No. 4,425,130, and others;
by creating more absorbency by utilizing either absorbing fibers or superabsorbing polymers, by varying the density inside and along the traditional absorbing sheet or with layers of varied materials, and others.
From this list of improvements it can be seen that the optimization of the product with increasing complexity and sophistication tends to make the product more and more expensive with respect to the benefit obtained, which consequently raises the price for the final consumer.
An examination of the reasons for the existence of leakage in external sanitary pads indicates that it is necessary to minimize the course of the vaginal discharge to the Point at which it meets the Product that will collect and retain such liquids. This is justified by the fact that any course allows the fluid to flow over the skin adjacent the place of discharge, to a greater or lesser extent, obviously depending, for instance, upon the viscosity and the surface tension of such a liquid. In this way, in some cases it can even fall out of the reach of the absorbing sheet and leak, thus causing discomfort, embarrassment and the consequent feeling of unsafety for the user. The conclusion is that a structure with an excellent intrinsic performance as regards absorption and leakage retention can function only from the moment at which the contact of the liquid with such a structure occurs, not before.